Repealing laws is much harder than passing new ones (both politically and procedurally). Depending on the law and location, you often need more votes to repeal than to pass.
Specifically for California, some ballot measures are harder to change/repeal than to pass in the first place[1].
I don't think Congress can write bills that are harder to repeal, but I know some states can. There are also states that abuse their own constitutions to accomplish the same thing, for example if a supermajority is required to amend the constitution.
